Echinodermata structures

Sialic acids comprise a family of derivatives of neuraminic acid (5-amino-3,5-dideoxy-D-g/jcero-D-ga/ cto-nonulosonic acid) occurring widespread in nature, especially in the animal kingdom. From an evolutionary point of view, they probably have a long history, dating back to precambrian times, as they have already been found in Echinodermata (chapter B). It took a number of years (1936-1962) to establish the structure of N-acetylneuraminic acid by chemical and enzymic means, as has been reviewed by Gottschalk (1972), Ledeen and Yu (1976) and Tuppy and Gottschalk (1972). 

Another structure so far found only in the Echinodermata is the disaccharide Fuca(l-4)Neu5Gca(2-) from sea urchin eggs (Hotta 1977) and the cuverian tubules of the sea cucumber Holothuria forskali (unpublished) again the sialic acid residue is internal. 

Kelecom, a., B. Tursch, and M. Vanhaelen Chemical Studies of Marine Invertebrates XIX. Glycosidic Chain Structure of Thelothurins A and B, Two New Saponins from the Indo-Pacific Sea Cucumber Thelenota ananas Jaeger (Echinodermata). Bull. Soc. Chim. Belg. 85, 277 (1976). 

In a similar way, Cd NMR spectroscopy helped to determine the cluster structures present in crustaceans, i.e., two M3S9 clusters of the (3-type [40,41,131], and echinodermata MTs [36,132]. In the latter MT family a M3S9 as well as a M4S11 cluster are observed in analogy to the vertebrate MTs, however, their occurrence within the amino acid sequence is reversed, i.e., the trinuclear (3-cluster is hosted by the C-terminal part of the protein while the tetranuclear a-cluster resides in the N-terminal part. 

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